chapter 12

At the normal resting potential of a typical neuron, its sodium-potassium exchange pump transports

3 intracellular sodium ions for 2 extracellular potassium ions

________ open or close in response to binding specific molecules

Chemically gated channels

________ nerves are nerves that connect to the brain.

Cranial

Which of the following is true about threshold for an action potential?

It is more positive than the resting potential

Sensory information from skeletal muscles travels over ________ fibers

Type A

The ________ division of the peripheral nervous system brings sensory information to the central nervous system.

afferent

________ carry sensory information to the CNS

afferent neurons

The part of the peripheral nervous system that carries sensory information to the CNS is designated

afferent.

The all-or-none principle states that

all stimuli great enough to bring the membrane to threshold will produce identical action potentials

The ________ principle states that the size and speed of the action potential are independent of the stimulus strength.

all-or-none

Neurons that are rare, small, and lack features that distinguish dendrites from axons are called

anaxonic

________ neurons are small and have no anatomical features that distinguish dendrites from axons.

anaxonic

Products from the soma of a neuron are transported to the synaptic terminals by ________ transport.

anterograde

IPSPs (inhibitory postsynaptic potentials)

are local hyperpolarizations

The buildup of depolarization when EPSPs arrive in rapid succession is called ________ summation

temporal

When a second EPSP (excitatory postsynaptic potential) arrives at a single synapse before the effects of the first have disappeared, what occurs?

temporal summation

The site in the neuron where EPSPs and IPSPs are integrated is the

axon hillock.

Which type of synapse is most common in the nervous system?

chemical

A postsynaptic neuron will have an excitatory postsynaptic potential (EPSP) when

chemically regulated sodium channels are open and sodium is diffusing into the cell.

If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?

chemically-regulated potassium channel

Branches that may occur along an axon are called

collaterals

The ________ division of the nervous system carries motor commands to muscles and glands.

efferent

In a(n) ________ synapse, current flows directly between cells.

electrical

The sum of the electrical and chemical forces acting on an ion is known as its

electrochemical gradient

The most common neuron of the nervous system is the

interneuron

________ are the most numerous type of neuron in the CNS

interneurons

If the permeability of a resting axon to sodium ion increases

inward movement of sodium will increase and the membrane will depolarize

The sodium-potassium ion exchange pump

moves sodium and potassium opposite to the direction of their electrochemical gradients

When pressure is applied to neural tissue, all of the following effects are possible except

neurons are triggered to divide

The same ________ can have different effects depending on the properties of the ________

neurotransmitter; receptor

Which of the following activities or sensations is/are not monitored by interoceptors?

sight

The tiny gaps between adjacent Schwann cells are called

nodes of Ranvier

Adrenergic synapses release the neurotransmitter

norepinephrine

The myelin sheath that covers many CNS axons is formed by

oligodendrocytes

The efferent division of the peripheral nervous system innervates ________ cells

skeletal muscle, smooth muscle, heart muscle, and glandular

When cholinergic receptors are stimulated,

sodium ions enter the postsynaptic neuron.

The ________ nervous system controls the skeletal muscles

somatic

The buildup of depolarization when EPSPs arrive at several places on the neuron is called ________ summation.

spatial

Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated

spatial summation

If the axon terminal of a motor neuron suddenly became permeable to calcium ion,

the motor end plate will be depolarized

A neuron that receives neurotransmitter from another neuron is called

the postsynaptic neuron

The minimum stimulus required to trigger an action potential is known as the

threshold

Ions can move across the plasma membrane in which of the following ways?

through voltage-gated channels as in the action potential, through passive or leak channels, by ATP-dependent ion pumps like the sodium-potassium exchange pump, and through chemically gated channels as in neuromuscular transmission

Which of the following types of nerve fiber possesses the fastest speed of impulse propagation?

type A

In a(n) ________ neuron, the dendrites and axon are continuous or fused

unipolar

Sensory neurons of the PNS are

unipolar

Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called

unipolar.

Neurotransmitters ready for release are stored in synaptic

vesicles

Any stimulus that opens a ________ ion channel will produce a graded potential

voltage-gated, chemically gated, sodium, and mechanically gated

Which of the following does not influence the time necessary for a nerve impulse to be transmitted?

whether or not the impulse begins in the CNS

Regions of the CNS with an abundance of myelinated axons constitute the ________ matter

white

Most CNS neurons lack centrioles. This observation explains

why CNS neurons cannot divide to regenerate damaged tissue

Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because

the endothelium of CNS capillaries forms a blood-brain barrier

When potassium channels open and the ions diffuse through the membrane,

the inside of the membrane will become more negative

If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except

the intracellular concentration of potassium ions will increase

The equilibrium potential for potassium ion occurs at approximately

-90mV

The following are the steps involved in transmission at a cholinergic synapse. What is the correct sequence for these events? 1. Chemically-gated sodium channels on the postsynaptic membrane are activated. 2. Calcium ions enter the synaptic terminal. 3. Acetylcholinesterase hydrolyzes acetylcholine. 4. An action potential depolarizes the synaptic terminal at the presynaptic membrane. 5. The pre-synaptic terminal reabsorbs choline. 6. Acetylcholine is released from storage vesicles by exocytosis. 7. Acetylcholine binds to receptors on the postsynaptic membrane. 8. Calcium ions are removed from the cytoplasm of the pre- synaptic terminal.

4, 2, 6, 7, 1, 8, 3, 5

The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization occurs. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization occurs.

4, 6, 7, 1, 2, 3, 5

Type ________ fibers have the largest diameter axons

A

The axoplasm of the axon contains which of the following? A) neurotubules B) mitochondria C) vesicles D) neurofibrils E) All of the answers are correct.

All of the answers are correct.

The function of the astrocytes in the CNS includes which of the following? A) adjusting the composition of the interstitial fluid B) guiding neuron development C) maintaining the blood-brain barrier D) repairing damaged neural tissue E) All of the answers are correct.

All of the answers are correct.

________ carry motor information to peripheral effectors.

Efferent neurons

Which of the following is not true regarding the establishment of a neuron's resting potential?

Electrical forces push sodium ions into the cell.

________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems

Internoceptors

How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate?

It would last indefinitely

________ channels open or close in response to physical distortion of the membrane surface

Mechanically gated

Clusters of RER and free ribosomes in neurons are called

Nissl bodies

________ monitor the position of skeletal muscles and joints

Proprioceptors

________ nerves are nerves that connect to the spinal cord

Spinal

Opioids relieve pain by blocking the release of

Substance P

Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons?

The axon would be unable to generate action potentials

How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron?

The neuron will only be capable of producing graded potentials

Which of the following statements about the action potential is false?

The rapid depolarization phase is caused by the entry of potassium ions

How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron?

The soma becomes unable to respond to changes in the distal end of the axon

Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration

Wallerian

In which of the following would the rate of impulse conduction be the greatest?

a myelinated fiber of 10-µm diameter

If the axolemma becomes more permeable to potassium ion,

a stronger stimulus will be required to cause an action potential

The period during which an excitable membrane cannot respond to further stimulation is the ________ period.

absolute refractory

Cholinergic synapses release the neurotransmitter

acetylcholine.

The largest and most numerous of the glial cells in the central nervous system are the

astrocytes

The neuroglial cells that participate in maintaining the blood-brain barrier are the

astrocytes.

The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity.

autonomic

The plasma membrane of an axon is called the

axolemma

The axon is connected to the soma at the

axon hillock

At a(n) ________ synapse, a neurotransmitter is released to stimulate the postsynaptic membrane

chemical

Neurons that have one axon and one dendrite, with the soma in between, are called

bipolar

________ neurons are short, with a cell body between dendrite and axon, and occur in special sense organs

bipolar

Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have what effect?

both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

Presynaptic facilitation by serotonin is caused by

calcium channels in the presynaptic membrane remaining open longer

The ion that triggers the release of acetylcholine into the synaptic cleft is

calcium.

The ________ nervous system is composed of the brain and spinal cord

central

Most neurons lack ________ and so are permanently blocked from undergoing cell division.

centrioles

Which of the following is not a possible drug effect on synaptic function?

change the type of receptor found in the postsynaptic membrane

Functions of astrocytes include all of the following except A) maintaining the blood-brain barrier. B) conducting action potentials. C) guiding neuron development. D) responding to neural tissue damage. E) forming a three-dimensional framework for the CNS

conducting action potentials

Integral membrane proteins that connect electrical synapses are called

connexons

A movement of charges in response to a potential difference is called

current

The sensory loss and muscle weakness associated with multiple sclerosis are a consequence of

demyelination.

A shift of the resting transmembrane potential toward 0 mV is called

depolarization

Opening of sodium channels in the axon membrane causes

depolarization

A threshold stimulus is the

depolarization necessary to cause an action potential

What triggers the release of acetylcholine from a synaptic terminal?

diffusion of calcium ions into the synaptic terminal

1) Which of the following is not a function of the nervous system? A) sense the internal and external environments B) integrate sensory information C) coordinate voluntary and involuntary activities D) direct long-term functions, such as growth E) control peripheral effectors

direct long-term functions, such as growth

Which of the following is a recognized class of opioid neuromodulators?

endorphins, enkephalins, endomorphins, and dynorphins

________ line the brain ventricles and spinal canal.

ependymal cells

________ provide information about the external environment

exteroceptors

EPSPs (excitatory postsynaptic potentials) occur when

extra sodium ions enter a cell.

Damage to ependymal cells would most likely affect the

formation of cerebrospinal fluid

In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by

forming a cellular cord that directs axonal regrowth

The effect that a neurotransmitter has on the postsynaptic membrane depends on the

frequency of neurotransmitter release, nature of the neurotransmitter, characteristics of the receptors, and quantity of neurotransmitters released.

Neuron cell bodies in the PNS are clustered together in masses called

ganglia

Which of the following is the most important excitatory neurotransmitter in the brain that is important in learning and memory?

glutamate

Regions of the CNS where neuron cell bodies dominate constitute the ________ matter

gray

Active neurons need ATP to support which of the following?

he movement of materials to the soma by axoplasmic transport, the synthesis of neurotransmitter molecules, the movement of materials from the soma by axoplasmic transport, and the recovery from action potentials

Voltage-gated channels are present

in the membrane that covers axons

Voltage-gated sodium channels have both an activation gate and a(n) ________ gate

inactivation

A stimulus that changes a postsynaptic neuron's membrane from resting potential to -85 mV is a(n) ________ stimulus

inhibitory

Ion channels that are always open are called ________ channels

leak

Extensive damage to oligodendrocytes in the CNS could result in

loss of sensation and motor control

Graded potentials

may be either a depolarization or a hyperpolarization

Which of the following is not involved in creating the resting potential of a neuron?

membrane permeability for sodium ions greater than potassium ions

Which of the following is not a function of the neuroglia?

memory

After a stroke, what type of glial cell accumulates within the affected brain region?

microglia

Small, wandering cells that engulf cell debris and pathogens in the CNS are called

microglia

________ neurons are the most common structural class in the CNS

mulipolar

Neurons that have several dendrites and a single axon are called

multipolar

The most abundant class of neuron in the central nervous system is

multipolar.

The presence of ________ dramatically increases the speed at which an action potential moves along an axon

myelin

Each of the following is an example of a synapse between neurons and effector cells except the junction between a neuron and a(n)

nerve cell

_______ account for roughly half of the volume of the nervous system

neuroglia

Compounds that alter the rate of neurotransmitter release by the presynaptic neuron or change the postsynaptic cell's response to neurotransmitters are called

neuromodulators

The basic functional unit of the nervous system is the

neuron

The cytoplasm that surrounds the nucleus of a neuron is called the...

perikaryon

The nervous tissue outside of the central nervous system composes the ________ nervous system.

peripheral

During repolarization of a neuron

potassium ions move out of the cell

The separation of positive and negative charges across the membrane creates a ________ difference, or voltage

potential

Which of the following is not a recognized structural classification for neurons? A) anaxonic B) bipolar C) multipolar D) pseudopolar E) unipolar

pseudopolar

After acetylcholinesterase acts, the synaptic terminal

reabsorbs the choline

The period during which an excitable membrane can respond again, but only if the stimulus is greater than the threshold stimulus, is the ________ period.

relative refractory

A change in the conditions in the synaptic terminal can influence the soma as a result of ________ transport

retrograde

The rabies virus travels to the CNS via

retrograde axoplasmic transport.

Rapid impulse conduction from "node" to "node" is called

saltatory propagation

Glial cells that surround the neurons in ganglia are

satellite cells

Which of the following is a type of glial cell found in the peripheral nervous system?

satellite cells

The neurilemma of axons in the peripheral nervous system is formed by

schwann cells

________ neurons form the afferent division of the PNS.

sensory

The site of intercellular communication between a neuron and another cell is the

synapse.

If the chemically gated sodium channels in the postsynaptic membrane were completely blocked,

synaptic transmission would fail

Axons terminate in a series of fine extensions known as

telodendria